There are a variety of well known processes used in large volume production. These known processes include die striking, casting and electroforming, all of which are used for producing metallic articles, and injection molding, which is generally used for producing plastic articles. These known production methods are capable of facilitating high volume, high speed production with excellent reproducibility. Using permanent-mold casting or injection molding techniques, for example, a single mold cavity may be used repeatedly to produce at a low cost a virtually unlimited number of indistinguishable articles of intricate detail and of any size.
While processes such as die striking and injection molding of parts for casting are generally recognized as being highly efficient manufacturing processes for precious metal manufacturing, there has been a recent trend toward the development of manufacturing processes having an even greater level of productivity and a decreased production cost.
In this regard, most improved manufacturing processes are directed at improvements in production equipment. There is, however, a practical limitation on the level of cost reduction made possible by means of improved machinery or industrial efficiency techniques. While productivity may be enhanced to maximize throughput by improving equipment design, at a certain level production costs can no longer be decreased. This is due to the fact that the largest cost component of a high volume manufacturing process of precious metal jewelry is the cost of the materials used in the production of a finished jewelry article.
While previous improvements in production processes have focused mainly upon improvements in the equipment used for the production of a particular article, or on the method of operating such equipment, there has been a general lack of advancement or improvement of production processes which are directed to modifying the manufactured article itself rather than modifying the equipment used for producing the article. For instance, by developing a process which minimizes the amount of raw materials (e.g., precious metals) used for production of an article, the production cost of the article can be substantially decreased. Despite this, few methods are known for reducing the amount of raw materials, and among the methods that are known there are serious limits to the application thereof to ring designs.
For example, several methods have been developed to reduce the amount of raw materials used for producing an article, each resulting in an article having a hollow construction in regions unexposed to appreciable external stress. By reducing the amount of material used in the finished article, the largest component of the production cost used for fabricating the article may be reduced, far in excess of that possible by simply enhancing production throughput.
One such method is electroforming, which is commonly used in the production of hollow metallic articles, notably various articles of jewelry, such as earrings, pendants, pins and bracelets--but not rings. Using electroforming techniques, a thin layer of a precious metal is deposited onto a chemically soluble substrate to form a desired article. After deposition of the metallic layer, the substrate is removed by a suitable chemical treatment, leaving only the thin metallic layer.
The electroforming process suffers from severe limitations in both the design and the type of articles which may be produced thereby. For example, electroforming techniques are suitable only for articles which are completely hollow in construction, and cannot be used to produce articles which are exposed to an appreciable external stress. While electroforming is capable of producing articles having intricate detail, articles produced by such a technique possess a very low tensile strength due to their hollow construction. This is the reason why rings are not produced using this technique.
The use of acid or water soluble wax inserts in mold cavities to mold partially or completely hollow articles is another method used for the reduction of production costs by reducing the amount of precious metal in the end product. According to this technique of molding with wax, commonly referred to as "waxing", a soluble wax core insert is placed in a mold cavity. Then a molten plastiwax (a plastic/wax substance) is injected into the mold cavity, filling the cavity and surrounding the core insert. The core insert is then removed to produce a plastiwax article having a hollow core.
The use of soluble wax core inserts is equally problematic. Difficulties in achieving the proper alignment of the insert and in preventing random movement or shifting of the insert during waxing or casting have plagued the use of inserts in waxing or casting processes for articles such as rings. As a result, the use of inserts has achieved only limited success and is generally limited to processes in which precision is of little concern or in which the volume of the insert is relatively small compared to the overall volume of the article in the region surrounding the insert.